In these studies we examine several biological membrane and surfactant systems and integral membrane proteins. A variety of Nuclear Magnetic Resonance (NMR) methodologies are employed: 1) Time resolved 35C1 NMR linewidth analyses will be used to follow the binding and release of chloride ions in the halorhodopsin light-driven chloride transport system. 2) 2H NMR powder pattern moment analysis will be used to assess the physical state of pulmonary surfactant as a function of lipid composition. 3) Paramagnetic relaxation and shift studies of solvent and ligand (inhibitor and steriod substrate) nuclei in the cytochrome P-450scc enzyme system will be used to explore its active site structure and membrane location. 4) 2H and 31P NMR powder patterns of the lipids and 1H and 13C spectral characteristics of small peptides in peptide-lipid bilayer mixtures will be used to examine, at an elemental level, lipid-protein interactions. Each of these studies requires the use of a sophisticated NMR spectrometer for extended periods of time. Two of them ((2) & (4)) require an instrument capable of performing NMR experiments on "solid" samples. The halorhodopsin study requires an optical system interfaced with the NMR spectrometer. The proposed instrument will enhance the research endeavors of the major users and its presence will serve to promote interactions within the Dept. of Physiology & Biophysics and within the California College of Medicine.